Method and apparatus for checking tool relief angle

ABSTRACT

A method and apparatus for determining the relief angle of the cutting edge on a helical cutting tool is provided by utilizing a sensing probe connecting the tool during relative movement between the probe and the tool in a first plane which can be readily mathematically converted to a functionally requisite angle in a second plate.

i it

Sttes Pag urz 1 Aug. 15, 1972 [54] METHOD AND APPARATUS FOR 2,620,65512/1952 Priest ..73/105 CHECKING TOOL RELIEF ANGLE 2,974,418 3/1961Stimson ..33/ 199 B [72] Inventor: William I. Kurz, Chicago, L 3,231,9822/1966 Rlbtchu ..33/75 R 60631 3,442,019 5/1969 Breltwelser et al..33/l74 P [73] Assignee: Illinois Tool Works Inc., Chicago,P'imwyExaminer-Williaml1MartinJrlll. Att0rneyRobert W. Beart [22] Filed:May 18, 1970 57 ABSTRACT [21] APPl- N04 38,302 A method and apparatusfor determining the relief angle of the cutting edge on a helicalcutting tool is 52 us. Cl. ..33/201, 33/199 B provided y utilizing asensing Probe connecting the [51] Int. Cl. ..G0lb 5/20 tool duringrelative movement between the probe and [58] Field of Search.....33/20l,199 B, 174 P; 73/105 the tool in a first plane which can be readilymathematically converted to a functionally requisite angle in [56]References Cited 3 second plate,

UNITED STATES PATENTS 10 Claims, 5 Drawing Figures 3,208,272 9/1965Hall, Jr. et al. ..73/l05 METHOD AND APPARATUS FOR CHECKING TOOL RELIEFANGLE BACKGROUND OF THE INVENTION 1. Field of the Invention Thisinvention is generally concerned with measuring the relief angle on acutting tool.

2. Description of the Prior Art Many methods and devices have beenconceived for measuring the relief angle on cutting tools. The reliefsurfaces fall generally into three major categories. Flat relief,concave relief and eccentric relief are the major configurations shownto effectively produce backoff clearances required in the cutting tool.The eccentric relief presents numerous problems for the accuratemeasurement of the relief surface angle thereof since it presents agenerally curved surface on a relatively thin land portion of thecutting too].

Examples of prior art methods and apparatus used for measuring thecutting tool geometry are found in patents to Ribich US. Pat. No.3,231,982 and Gase U.S. Pat. No. 2,648,138. The Ribich method involvesplacing a flat edge along the relief surface in the transverse plane ofthe cutting tool and sighting along the longitudinal axis of the cuttingtool in an effort to read the angular relationship of the reliefsurface. The patent to Gase similarly discloses the use of a straightedge placed on the relief surface in a transverse plane to the cuttingtool and sighting through an optical instrument in an attempt toaccurately read the clearance angle. These methods typify the priorprocedure used in determining the relief angle and do not adequatelysolve the problems inherent in measuring an eccentric relief surface.When it is attempted to measure the effective or tangential relief angleof such a relief surface, which is a convex curve in the transverseplane of the tool, the straight edge of the prior art method must beviewed by the eye in a transverse plane to the curvature of the primaryrelief surface. The eye is asked to place the testing straight edge in atransverse plane tangent to the archimedean spiral at the peripheralcutting edge. Under the above circumstances, there is uncertainty when across hair of a microscope or a line on a comparative screen or astraight edge is matched in this way against a curved surface. It hasbeen found that different operators or inspectors will get differentvalues for the primary relief angle using the prior art method andapparatus. The measuring difficulty is compounded by the fact that theprimary relief land, which determines the cutting ability of a cuttingtool, is a relatively narrow surface and therefore, it is obvious thatmatching a straight edge or a line to such a narrow surface to determineits inclination requires skill, experience and care. When the actualsmall relief surface is curved, the difficulty of getting accurateresults is even more pronounced.

SUMMARY OF THE INVENTION It is therefore an object of the invention toprovide a method and apparatus for accurately measuring the clearanceangle on cutting tools.

It is another object of this invention to provide a measuring devicewhich requires a minimum of human judgement to determine the reliefangle on cutting tools.

It is another object of this invention to provide an apparatus andmethod for accurately determining the relief surface angle when therelief surface is a narrow, convex surface.

It is still another object of this invention to provide an apparatus andmethod capable of determining the actual relief angle in the transverseplane of the tool by measuring a relief angle in an axial plane of thecutting tool.

Other objects and advantages of the present inven- 'tion areaccomplished by a method and apparatus which uses a sensing probe tomeasure the inclination of a relief surface in the axial plane of thecutting tool which measurement can be readily mathematically convertedto the functionally requisite angle in the transverse plane. The methodof invention involves placing a sensing probe on the relief surface tobe measured and moving the tool and the probe relative to one another inan axial plane of the tool, thus tracing a relatively long path over therelief surface and thereafter recording the relationship between theaxial distance traveled and the vertical displacement of the probe on arecording device. The recording device utilizes a graph paper whichmoves proportionally to the relative distance moved in the axial planeof the probe and a recording pen associated with the movable graphindicates the vertical displacement of the probe for an associatedmovement in the axial plane of the probe. Thus an accurate display isgenerated representative of the relief surface angle measured in theaxial plane of the tool. The displayed angle can readily be converted tothe desired relief surface angle in the transverse plane of the tool bya simple computation which is dependent on the particular helix angle ofthe cutting tool. Alternatively, the conversion may be made by using aspecially designed slide rule.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of theapparatus of the present invention with the components thereof in placewhich are necessary for checking the relief angle in the axial plane ofthe cutting tool;

FIG. 2 is generally a plan view of the relief surface to be measured ona cutting tool illustrating the path of measurement of both the presentinvention and the prior art;

FIG. 3 is a partial end view of a cutting tool showing a prior artmethod of measuring the relief angle;

FIG. 4 is an illustration of one form of display showing therelationship between the axial movement of the probe and the verticaldisplacement of the probe; and

FIG. 5 is an illustration of a slide rule to be utilized in conjunctionwith the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring specifically to FIG. 1there is shown an apparatus for checking the relief surface angle of ahelical cutting tool indicated by the reference numeral 10. Theclearance checker 10 includes a base 14 which supports a slotted guide20 and a mounting platform 50 in a side-by-side relationship. A cuttingtool 12 is mounted on the apparatus for measurement by means of anaxially movable mounting block 16 and a complementary U-shaped mountingclamp 18. The tool is placed in a V-shaped groove in the mounting blockand is securely positioned thereto by tightening a fastening elementsuch as threaded element 52 associated with the mounting clamp 18. Themounting block 16 is operatively mounted on the slotted guide whichallows the block and associated tool to be moved axially for initiallypositioning the tool for measurement.

A mounting platform 50 includes a horizontal positioning platform 30which is controlled by a crank 32. This horizontal platform and crankthus serve as a means for axially feeding an associated testing probeover the surface of a cutting tool. A sensing probe 22 is mounted foroperation in a mounting element 28 which is operatively associated witha radial adjustment stand 26. The radial adjustment stand operatessimilar to the horizontal positioning platform in that the stand alsoincludes a feed element operated by a crank 34. Thus the probe 22 can bemoved into and out of contact with the cutting tool while remaining inan axial plane of the cutting tool by selectively operating the crank 34and moving support 28 up or down. The probe 22 sensitively records avertical displacement of the sensing tip 24 as the probe progressesaxially of the tool along the relief surface 44. These displacements arerecorded and displayed through the use of a recorder similar to thatshown in U.S. Pat. Nos. 2,261,093 and RE 22,1 10. This type of recorder,denoted generally as 36 in FIG. 1, includes a tracing pen 38 andautomatically fed graph paper 40. The movement of the pen 38 beinggoverned by the displacement impulses which are fed from the sensing tip24 through an interconnecting cable 42. The movement of the paper isdirectly associated with the axial movement of the probe so that theresulting display will accurately represent the relationship between theaxial movement of the probe and the vertical displacement thereof.

In operation, the tool to be measured is secured on the mounting blockand clamp while the sensing probe is positioned on the trailing edge ofthe relief surface land 44 by radially positioning the probe mountthrough the radial feed means 34. When the probe is in position, it isthen moved in an axial plane of the tool by engaging the crank 32 whichmoves the horizontal positioning platform upon which is mounted theradial adjustment stand, the probe mount and sensing probe. As the probemoves toward the cutting edge 55, in the direction shown as A in FIG. 2,the sensing tip 24 is displaced in accordance with the relief angle onthe cutting tool. This displacement is reflected by the movement of therecording pen 38 on the automatically fed graph 40 which results in thedisplay illustrated in FIG. 4.

From FIG. 2 it is shown that the path of travel A of the probe in thepresent invention is significantly longer, and presents a larger spacefrom which to measure the relationship between the vertical displacementand the axial distance, than is traditionally presented by the movementin the B direction representative of the prior art method. Inconjunction with this, FIG. 3 shows an end view of a cutting tool,having a relief surface 48, the angle of which is to be measured. Thetypical prior art method involves the placement of a straight edge 46 onthe surface 48 in an attempt to measure the angle of the surface 48.FIG. 3 points out the problems inherent in this type of an operation.For example, the relief surface 48 is of an eccentric form whichpresents a curved surface to be measured and therefor renders itdifficult to obtain an accurate reading of the angle of the surface byusing a straight edge such as 46.

The relief surface commonly called eccentric" generally presents acurved surface when viewing the tool in a transverse plane. Thiseccentric surface is, however, actually part of an archimedean spiralwhich presents a straight line surface in the axial plane of the cuttingtool, such as in the plane associated with the path of travel A in FIG.2. Therefore, the travel of the sensing probe along the path A willproduce a straight line representation of the relationship between thevertical displacement and the axial distance traveled as represented bythe graph in FIG. 4. Thus, while the path of contact from point a" topoint h" in FIG. 2 would be represented as a curved path, the path ofcontact from point 0" to point c" would be represented as a straightline path. The straight line path from point a to point 0 is susceptibleto easy interpretation into an angular relationship. The sharp drop inthe line in FIG. 4 represents the probe reaching the extremity of theland and losing contact with the cutting edge 55.

From the above description it is apparent that the display generated bythe recorder 36 ostensibly represents the relief surface angle of thecutting tool measured in the axial plane of the tool. Since the commonreference to the relief surface angle is in a transverse plane to thetool, further conversion of this display may be desired. In accordancewith the concept of the archimedean spiral, a conversion of themeasurement of the relief angle in the axial plane of the tool isdependent on the helix angle of the cutting edge of the tool. Thisrelationship is represented as follows:

Tangent of relief angle in transverse plane Tangent of relief angle inaxial plane Tangent of helix angle For example, viewing FIG. 4, Axrepresents the distance traveled in the axial direction of the sensingprobe while Ay represents the vertical displacement of the sensing probeassociated with the axial distance. The slope of the line represented inFIG. 4, Ay/Ax thus represents the tangent of the relief angle measuredin the axial plane of the tool, as in direction A of FIG. 2. If, forexample, the slope represented by Ay/Ax were to be 0.1000, the measuredangle of the relief surface in the axial plane would be 5 43'. For acutting tool having a helix angle of 30, the tangent of the relief anglein the transverse plane would be represented by Tangent 543 .1000

Tangent; 30 .5773

Thus, the tangent of the relief angle in the transverse plane would bethe arctangent of 0.17321 or 9, 50'

The conversion of the measured angle in the axial plane of the tool tothe angle in the transverse plane of the tool is simplified by the useof a slide rule apparatus shown in FIG. 5. This type of a slide ruletakes the relationship between the drop and the travel or Ay and Axrespectively and converts this relationship directly into the degree ofclearance angle in the transverse plane. It should be noted that theother variable involved, the helix angle, is also utilized in theultimate conversion of the raw data to the desired relief cleance anglein utilizing the slide rule.

Therefore, it will be seen that an apparatus and method has beenprovided for efficient, accurate determination of the relief angle of acutting tool utilizing measurement in the axial plane of the tool andsubsequent conversion to a true value in the transverse plane.

It should be recognized, that while the apparatus and method have beendescribed with particular reference to the measurement of the peripheralangle when the relief surface is an archimedean spiral, it has also beenfound that the same novel approach of checking and charting in the axialdirection can be used to evaluate relief surfaces having other forms.Therefore, flat, and both convex and concave arcuate relief forms can beaccurately charted and analyzed. This advantage comes from the simplenature of the device, its repeatability within narrow limits, and itspictorial presentation in chart form of the results.

I claim: 1

1. A method of determining the relief angle of a helical cutting toolhaving an eccentric relief surface behind its cutting edges comprisingthe steps of:

mounting the tool to prevent its rotation,

moving the tool and a relief surface engaging probe relative to eachother in the axial direction of the tool,

maintaining said probe in engagement with said tool for a predetermineddistance along a line on said relief surface of said tool which lies inthe axial plane of the tool and converting the amount of displacement ofthe probe in a direction perpendicular to the axis of the tool whichtakes place during the predetermined movement of said probe in an axialdirection, into the value of the eccentric relief surface angle behindthe cutting edge of the tool in a plane transverse to the longitudinalaxis of the tool.

2. A method of measuring the edge relief angle of a helical cutting toolin accordance with claim 1 wherein the probe is moved in an axial planerelative to the tool.

3. Amethod of measuring the edge relief angle of a helical cutting toolin accordance with claim 1 including the steps of:

automatically generating a display showing the relationship of thevertical displacement of the probe to the distance of movement of theprobe in an axial direction on a recording device for conversion intorelief surface angle in the transverse plane of the tool.

4. An apparatus for measuring the relief angle of an eccentricallyrelieved helical cutting tool comprising a frame, first mounting meanson the frame for mounting the tool against rotation, second mountingmeans on the frame for mounting the tip of a probe member in engagementwith a relief surface on the tool, radial adjustment means for movingsaid second mounting means and said tool relative to each other so thatthe tip of said probe may be brought into and out of engagement withsaid tool in a radial direction and within an axial plane of said tool,feed means for moving said first and second mounting means relative toeach other in the direction of the axis of said cutting tool so that thetip of said probe member remains within said axial plane, said tip ofsaid probe member being displaceable relative to said second mountingmeans in response to changes in the distance between the tool axis andthe rehe surface of said tool during the relative movement of said feedmeans, and means for producing an indication of the value of theeccentric relief angle lying in a plane transverse to the longitudinalaxis of the tool wherein said indicating means is dependent on andresponsive to the displacement of the tip of said probe which occursduring a predetermined amount of movement of said probe in the planeincluding the longitudinal axis of the tool.

5. An apparatus in accordance with claim 4 which includes guide meansfor axially positioning the first mounting means on the frame.

6. An apparatus in accordance with claim 4 wherein the radial adjustmentmeans includes a vertical slide and vertical feed means.

7. An apparatus in accordance with claim 4 wherein the means for movingthe first and second mounting means relative to each other includes ahorizontally movable platform.

8. An apparatus in accordance with claim 4 wherein the display meansincludes a recorder operatively connected to the probe member.

9. An apparatus in accordance with claim 8 wherein the recorder includesa chart which is movable in conjunction with the axial movement of theprobe and a

1. A method of determining the relief angle of a helical cutting toolhaving an eccentric relief surface behind its cutting edges comprisingthe steps of: mounting the tool to prevent its rotation, moving the tooland a relief surface engaging probe relative to each other in the axialdirection of the tool, maintaining said probe in engagement with saidtool for a predetermined distance along a line on said relief surface ofsaid tool which lies in the axial plane of the tool and converting theamount of displacement of the probe in a direction perpendicular to theaxis of the tool which takes place during the predetermined movement ofsaid probe in an axial direction, into the value of the eccentric reliefsurface angle behind the cutting edge of the tool in a plane transverseto the longitudinal axis of the tool.
 2. A method of measuring the edgerelief angle of a helical cutting tool in accordance with claim 1wHerein the probe is moved in an axial plane relative to the tool.
 3. Amethod of measuring the edge relief angle of a helical cutting tool inaccordance with claim 1 including the steps of: automatically generatinga display showing the relationship of the vertical displacement of theprobe to the distance of movement of the probe in an axial direction ona recording device for conversion into relief surface angle in thetransverse plane of the tool.
 4. An apparatus for measuring the reliefangle of an eccentrically relieved helical cutting tool comprising aframe, first mounting means on the frame for mounting the tool againstrotation, second mounting means on the frame for mounting the tip of aprobe member in engagement with a relief surface on the tool, radialadjustment means for moving said second mounting means and said toolrelative to each other so that the tip of said probe may be brought intoand out of engagement with said tool in a radial direction and within anaxial plane of said tool, feed means for moving said first and secondmounting means relative to each other in the direction of the axis ofsaid cutting tool so that the tip of said probe member remains withinsaid axial plane, said tip of said probe member being displaceablerelative to said second mounting means in response to changes in thedistance between the tool axis and the relief surface of said toolduring the relative movement of said feed means, and means for producingan indication of the value of the eccentric relief angle lying in aplane transverse to the longitudinal axis of the tool wherein saidindicating means is dependent on and responsive to the displacement ofthe tip of said probe which occurs during a predetermined amount ofmovement of said probe in the plane including the longitudinal axis ofthe tool.
 5. An apparatus in accordance with claim 4 which includesguide means for axially positioning the first mounting means on theframe.
 6. An apparatus in accordance with claim 4 wherein the radialadjustment means includes a vertical slide and vertical feed means. 7.An apparatus in accordance with claim 4 wherein the means for moving thefirst and second mounting means relative to each other includes ahorizontally movable platform.
 8. An apparatus in accordance with claim4 wherein the display means includes a recorder operatively connected tothe probe member.
 9. An apparatus in accordance with claim 8 wherein therecorder includes a chart which is movable in conjunction with the axialmovement of the probe and a pen which is responsive to the radialdisplacement of the probe whereby the pen indicates on the chart theradial displacement of the probe along a corresponding axial movement.10. An apparatus in accordance with claim 8 wherein the recorderincludes means for tracing a line representing the relationship betweenthe axial movement of the probe and the radial displacement of the probethereby providing an effective representation of the relief angle of thetool measured in an axial plane.